Is this a worth upgrade?

The 5N is a big upgrade in ease of use with the touch screen. You will probably get shots with it you miss with your current set up. It will make you a better photographer. I tend to like a zoom for the versatility. Then add special purpose single focal length lenses.

Second option is to wait for the 5R and get the superb new focusing system, but if that is not an issue on your 3, go for the 5N.